Adjustable double-acting damper

ABSTRACT

A dasphpot damper for acting between two objects subject to move toward and away from one another including a housing including an elongated cavity, a piston mounted within the housing cavity for reciprocating movement therealong and dividing the cavity into two variable-volume, hydraulic fluid chambers, and a network of passages permitting hydraulic fluid to flow between the two variable-volume chambers as the housing and piston move relative to one another in response to relative movements between the two objects utilizes unitary flow control cartridge mounted within the housing and defining a passageway through which hydraulic fluid is forced to flow when passing between the two variable-volume chambers. The flow control cartridge also includes a check valve device associated with the passageway for controllably restricting the flow of hydraulic fluid in one direction through the passageway and for permitting substantially unrestricted flow of hydraulic fluid in the other direction through the passageway. By controlling the flow of hydraulic fluid through the passageway in the one direction, the damping effect of the damper is controlled. The flow control cartridge can be constructed so as to provide either an adjustable or fixed restriction to the hydraulic fluid flow in the one direction.

This is a continuation of co-pending application Ser. No. 737,326 filedon May 23, 1985 now U.S. Pat. No. 4,709,791 issued Dec. 1, 1987.

BACKGROUND OF THE INVENTION

This invention relates, generally, to devices for damping or cushioningthe movement between two objects moving relative to one another, andrelates more particularly to a new and improved dashpot type of damper.

The type of damper with which this invention is concerned commonlyincludes a housing assembly defining an elongated cavity for containinghydraulic fluid and a piston assembly having a head received by theelongated cavity for sliding movement in either of two directionstherealong. The housing assembly is connectable to one of two objectsmovable toward or away from one another, and the piston assembly isconnectable to the other of the two objects. The piston head is arrangedin the elongated cavity so as to separate the cavity into twovariable-volume chambers, and the housing assembly includes a network ofhydraulic fluid flow passages in flow communication with the first andsecond chambers. As the two objects move toward one another, the pistonmoves in one direction relative to and along the cavity to forcehydraulic fluid through the flow passages from one of thevariable-volume chambers to the other. Similarly, as the two objectsmove away from one another, the piston moves in the other directionrelative to and along the cavity to force hydraulic fluid through theflow passages from said other of the varible-volume chambers to said onechamber. For purposes of adjusting the damping or cushioning effect of adamper of the aforesaid described type, the damper includes adjustmentmechanisms for varying the size or configuration of its flow passages tothereby vary the flow characteristics of hydraulic fluid moving betweenthe two variable-volume chambers.

In the past, damper selection required extensive engineering time todetermine the proper parmeters under which a damper could best beutilized, with extensive testing, modification and re-testing.Accordingly, it would be highly desirable to provide a damper whichsubstantially reduces complex motion analysis by allowing the user todetermine an optimum setting, and then lock the damper in that positionwith a plug-in type self-contained unit, the unit allowing damping to beprogrammed or pre-determined for tension, compression or both, and theunit enabling the damper to be adjustable in compression and free-flowin tension or adjustable in tension and free flow in compression orboth.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a new and improveddashpot type damper.

Another object of the present invention is to provide such a damperhaving improved means for controlling the damping effect of the damper.

Still another object is to provide such a damper wherein the cushioningof movement between two objects toward and away from one another can beindependently controlled.

Yet still another object of the present invention is to provide such adamper having damping-adjustment means which are easily accessible.

It is a more particular object of the present invention to provide sucha damper which allows the user to determine an optimum setting and thenlock the damper in that setting with a readily accessible, plug-in typeself-contained unit which allows the damping to be programmed orpre-determined for tension, compression or both.

It is more particular object of the present invention to provide such adamper having a readily accessible, plug-in type self-contained unitwhich enables the damper to be adjustable in compression and free-flowin tension or adjustable in tension and free-flow in compression orboth.

A further object of the present invention is to provide such a damperwhich is economical to manufacture and effective in operation.

This invention resides in a new and improved damper for acting betweentwo objects subject to relative movement, for example toward and awayfrom one another.

The damper comprises piston means, housing means and hydraulic fluidflow control means. The piston means includes a head and a rod connectedto the head for securement one of the two objects. The housing includesmeans for securement to the other of the two objects and includes meansdefining an elongated cavity for containing hydraulic fluid. The pistonhead is received by the elongated cavity so as to separate the cavityinto first and second chambers and is adapted to slidably move relativeto and along the elongated cavity and thereby vary the volumes of thefirst and second chambers in response to relative movement between thetwo objects connected to the housing means and piston means. The housingfurther includes means defining an access opening, a first passage, anda second passage wherein the first chamber communicates with the accessopening through the first passage and the second chamber communicateswith the access opening through the second passage. The hydraulic fluidcontrol means includes a body sealingly accepted by the access openingand defines a passageway through the body providing flow communicationbetween the first and second passages and thereby providing a flow pathfor hydraulic fluid forced to exit one of the first and second chambersas the volumes of the chambers are varied by the relative movement ofthe two objects. The flow control means further includes meansassociated with the defined passageway for controlling or metering theflow of hydraulic fluid in one direction therethrough so that ashydraulic fluid is forced to flow through the passageway in said onedirection, the damping effect of the damper is controlled.

In accordance with this invention, the flow control means is aself-contained unit or cartridge which can be easily separated ordetached from the remainder of the damper. Such features permit the flowcontrol means to be cleaned, repaired or modified with no disassembly ofthe remainder of the damper. Furthermore, such features accommodate thereplacement of one flow control means which provides preselected fluidflow characteristics with another flow control means which providealternative fluid flow characteristics. Still further, since the flowcontrol means effectively define a conduit portion of the flow path forhydraulic fluid moving between the first and second chambers, thedefined conduit portion can be removed and altered to vary or adjust thedamping effect of the damper.

In another aspect of this invention, the flow control means is a firstflow control means for controlling hydraulic fluid flow in one directionbetween the first and second chamber, the housing includes meansdefining a second access opening arranged in flow communication with thepassageway of the first control means, with the first passage and withthe second passage, and the damper further includes a second hydraulicfluid flow control means for controlling hydraulic fluid flow in thedirection between the first and second chamber opposite said onedirection. Because the first and second control means are independentfrom one another, the damping effects of the damper as two objects movetoward one another and as the two objects move away from one another canbe independently controlled in tension and compression.

Other objects and advantages of this invention will become apparent uponreading the ensuing description with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a damper constructed inaccordance with this invention.

FIG. 2 is a cross-sectional view taken about on lines 2--2 of FIG. 1;

FIG. 3 is a longitudinal cross-sectional view of an adjustable hydraulicfluid flow control cartridge of the FIG. 1 damper drawn to a slightlylarger scale;

FIG. 4 is an end elevational view of the damper of FIG. 1 and taken fromthe right hand end as viewed in FIG. 1;

FIG. 5 is a longitudinal cross-sectional view similar to FIG. 3illustrating a fixed hydraulic fluid flow control cartridge.

FIG. 6 is a fragmentary view similar to that of FIG. 1 illustrating analternative damper embodiment utilizing an adjustable flow controlcartridge of FIG. 3 and a fixed flow control cartridge of FIG. 5.

FIG. 7 is a fragmentary longitudinal cross-sectional view similar toFIG. 3 illustrating a plug for an access opening of the FIG. 1 damper.

FIG. 8 is a view showing in block diagram form a control circuit forremote adjustment of the damping effect of the FIG. 1 damper.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

Referring now to the drawings in greater detail and considering firstFIG. 1, there is shown a double-acting, linear tension and compressionmotion hydraulic damper, generally indicated 10, according to thepresent invention. The damper 10 includes housing means 12, a pistonassembly 14, and hydraulic fluid flow control means 16 for controllingthe flow of hydraulic fluid through the damper 10. For purposes ofmounting the damper 10 between two distal objects (not shown) subject tomove toward or away from one another, the housing means 12 includes afirst clevis 20 and the piston assembly 14 includes a second clevis 22.Movement of the first clevis 20 and second clevis 22 toward or away fromone another force the piston assembly 14 to move relative to and alongthe housing means 12 to thereby force damping fluid to flow through anetwork of passages, hereinafter described, in the housing means from ahigh pressure region to a lower pressure region. Between the high andlower pressure regions, the hydraulic fluid is routed through thecontrol means 16 for purposes of controlling flow characteristics of thedamping fluid and thereby controlling the damping effect of the damper10.

The housing means 12 includes a cylindrical outer sleeve-like shell 24having two opposite ends 26, 28 and a manifold 30 fixedly attached toone end 28 of the sleeve-like shell 24. The shell 24 is formed of asuitable material, such as aluminium, and defines a relatively largecentral bore or region 32 extending from one end 28 of the shell 24 andalong a substantial portion of the length of the shell 24. The end 28 ofthe shell 24 is substantially closed by the manifold 30. Included at theother end 26 of the shell 24 is a relatively thick end portion 34defining an interior wall 36. The end portion 36 further defines acentral through-bore 38 and a circular outer end recess 40 as shown inFIG. 1 of slightly larger diameter than that of the bore 38.

Positioned within the shell bore 32 and adjacent the shell end 26 is abearing retainer 42 and a sleeve bearing 44. The bearing retainer 42 isconstructed of steel and has a retainer body which is closely receivedby the shell bore 32. The retainer 42 includes two opposite ends 46,48and defines a central through-bore 50, a slightly larger bore 52extending inwardly of the retainer body from the retainer end 48 and acircular recess 54 extending inwardly of the retainer body from theretainer end 46. As shown in FIG. 1, the end 46 of the retainer 40 abutsthe interior wall 36 of the shell end 26 and the sleeve bearing 44 isclosely received by the retainer bore 52. The end 48 of the retainerbody includes a reduced end portion 56 defining a shoulder 58.

Referring to FIGS. 1 and 2, the housing means 12 further includes anelongated inner shock tube 60 positioned within the shell bore 32. Theshock tube 60 includes two opposite ends 62,64, is constructed ofaluminium and has a cross section (FIG. 2) which resembles the shape ofa teardrop. A central through-bore 66 is defined in the tube 60 and aparallel bore 68 is defined in a portion of the tube 60 positionedadjacent the through bore 66. The bore 68 extends inwardly of the tubebody from the tube end 64 and is of smaller diameter than thethrough-bore 66. An aperture 70 is spaced a short distance from the tubeend 62 and permits the interior of the bore 66 to communicate with theinterior of the bore 68. The tube end 62 is closely fitted about thereduced end portion 56 of the retainer 42 for attachment thereto, andthe tube 60 and bearing retainer 42 are appropriately sealed with "O"rings 72,74.

The housing means 16 also includes an accumulator having a cavity,indicated 75, provided by the space S defined between the outer wall ofthe shock tube 60 and the inner wall of the shell 24. In accordance withthis invention, a relatively thick layer of closed cell foam material 77is supported within the accumulator cavity 75 for a purpose which willbe set forth hereinafter. More specifically, the layer of foam 77 iswrapped about the shock tube 60 so as to cover a substantial portionthereof and held thereagainst with "O" rings 79,79.

As shown in FIG. 1, the manifold 30 includes a substantially cylindricalbody 76 having two opposite ends 78,80 and an exterior sidewall,indicated 82, and is constructed of a suitable material, such as steel.The manifold end 80 of the body 76 includes a boss-like projecting endportion 84 having two diametrically opposed flat surfaces 84,86 and athrough-bore 90. It will be understood that the damper clevis 22,introduced above, is provided by the boss-like end portion 84 of themanifold body 76.

The manifold body 76 further includes a series of parallel passagewaybores 92,94 and 96 extending into the manifold body 76 from the manifoldend 78 and two access openings or bores 98 and 100 opening out of thesidewall 82 of the manifold body 76. Each access opening 98 or 100includes a portion adjacent the sidewall 82 which is internally-threadedfor a reason which will be apparent hereinafter. As best shown in FIG.1, the passageway bore 94 opens into the access opening 98, and thepassageway bore 96 opens into the access opening 100.

As shown in FIG. 1, the manifold bore 92 is located in the manifold body76 so as to communicate with each access opening 98 or 100, and a reliefvalve 104 or restrictor is supportedly mounted within the mouth of thebore 92. The manifold bore 94 is slightly offset from the center of themanifold body 76 as the body 76 is viewed in cross section and opensinto the access opening 98. The manifold bore 96 opens into the accessopening 100, and an apertured alignment pin 106 is supported within themouth of the bore 96.

With reference still to FIG. 1, the end 78 of the manifold body definesa circular recess 108 within which is closely received a hollowcylindrical bushing member 110. The bushing member 110 is so arranged inrelationship to the manifold body 76 that the manifold bore 94 opensinto the hollow interior indicated 112 of the bushing member 110. Theouter wall, indicated 116, of the bushing member 110 has a diameterwhich is slightly smaller than that of the shock tube bore 66.

The end 78 of the manifold body 76 is closely received by the end 28 ofthe housing shell 24 and is sealed there by an "O" ring 114. Themanifold body 76 is so oriented in relationship to the housing shell 24and shock tube 60 that the manifold bore 92 communicates with theaccumulator cavity 75 through the relief valve or restrictor 104 and themanifold bore 96 communicates with the shock tube bore 68 through thealignment pin 106. The manifold bore 94 communicates with the interior112 of bushing 110. The bushing 110 is closely received by the centralbore 68 of the shock tube 60 and sealed therein with the "O" ring 118.

The piston assembly 14 includes a head 120, an elongated rod 122, andthe clevis 22, introduced above. The elongated rod 122 has two oppositeends 124,126 and is of such cross-sectional dimension to be closelyreceived by the sleeve bearing 44. The rod end 126 is internallythreaded, as shown in FIG. 1, and the rod end 124 is provided with athrough-aperture 128, as shown. The clevis 22 has a body 130 defining acircular recess 132 closely accepted about the rod end 124. The clevis22 and rod end 124 are joined by a shanked fastener 134 extendingthrough the rod aperture 128 and aligned openings in the clevis 22. Forpurposes of fastening the clevis 22 to one of the two objects subject tomove toward or away from one another, the clevis body 130 includes athrough-bore 136.

The piston head 120 includes a body defining two opposite faces 138,140and of such size to be received within the cavity 66 of the shock tube60 for sliding movement therealong. The head 120 includes a circularrecess 142 extending into the body of the head 120 from the face 138whereupon it meets a through-bore 144 for receiving the shank of thefastener 146. The recess 142 of the head 120 is accepted about the rodend 126 and the fastener 146 is threadably accepted by the threads ofthe rod end 126 so that the head 120 is held upon the rod 122 betweenthe head of the fastener 146 and the rod end 126. The body of the head120 further defines a series of axially spaced annular grooves in theouter surface of head 120 and extending therearound within which apiston ring 150 and piston seals 152,152 are positioned for sealing thespace between the walls of the cavity 75 and the piston head 120. Forpurposes of sealing between the piston rod 122 and housing means 12, rodseals 154,154 are positioned within recesses 40 and 54 of the housingshell 24 and bearing retainer 42, respectively.

It will be understood that the piston assembly 14 is slidably mountedwithin the housing means 12 for reciprocating movement of the pistonhead 120 relative to the elongated cavity 66 as the two objects to whichthe damper 10 is connected move toward and away from one another. Itwill also be understood that the piston head 120 effectively separatesthe cavity 66 into a first variable-volume chamber 67 and a secondvariable-volume chamber 69 with the face 138 of the head 120 defining awall of the first chamber 67 and the face 140 of the head 120 defining awall of the second chamber 69. As movement of the piston head 120relative to the cavity 66 increases the volume of the first chamber 67,the volume of the second chamber 69 decreases and vise-versa. It willalso be understood, however, that since the piston rod 122 displacesvolume only in the first chamber 67 and not the second, as the pistonhead 120 reciprocates within the cavity 66, the rate of change of thevolumes of the first and second chambers 67 and 69 are unequal.

With reference to FIGS. 1 and 3, the hydraulic fluid flow control means16, 17 in accordance with the present invention, are identical and oneof the flow control means, for example flow control means 16, is shownin FIG. 3 and is provided by an elongated cartridge body 172, a movableflow control element in the form of spherical ball 174 and adjustmentmeans 176. The body 172 is of such shape and size to be sealinglyaccepted by either of the access openings 98 or 100 and includes anexternally threaded portion 178 adapted to be threadably accepted by theinternal threaded of the access opening thereof. "O" rings 180 and 182positioned about the cartridge body 172 contribute to the seal betweenthe body 172 and openings 98 or 100.

The cartridge body 172 defines an elongated open region 184 extendingfrom one end of the body 172 to the other. The opening 184 includes anupper or passageway portion 186, as shown in FIG. 3, and a lower orsupporting portion 188, as shown in FIG. 7, within which the adjustmentmeans 176 are supported. The supporting portion 188 of the opening 184is internally-threaded for a reason which will be hereinafter apparent.The body 172 further includes a transverse through bore 190 intersectingthe passageway portion 186 of the opening 184.

In accordance with the present invention, the passageway portion 186 ofthe body opening 184 defines a ball chamber 192 having first and secondends 194 and 196, respectively, which are fluid inlets or outletsdepending upon the direction of fluid flow as will be explainedpresently. The spherical ball 174 is loosely received or captured by theball chamber 192 and is coated with resilient elastomer 175, for exampleurethane, to provide a soft seat and effective seal. The ball 174 is ofsuch size and shape that if a fluid pressure differential exits betweenthe inlet and outlet ends 194 and 196, the ball 174 is biased toward thechamber end having the lower fluid pressure. The end 194 includes acontoured, conical-shaped surface 198 defining a fluid opening having asmaller diameter than that of the ball 174 so that the ball 174 can seaton surface 198 and is prevented from passing out of the ball chamber 192through the end 194. The opposite end 196 is relatively large indiameter, and a stop means in the form of pin 200 is supportedtransversely across the end 196 to prevent the ball 174 from passing outof the chamber 192 through the end 196.

The adjustment means 176 includes a plug 202 having a knob portion 204,a threaded securement portion 206 and an elongated stem portion 208. Thethreaded securement portion 206 is threadably received by the threadedsupporting portion 188 of the cartridge body 172 and can be rotatedtherein by means of the knob portion 204. The stem portion 208 is ofsuch shape and size to be received by the opening of the ball chamberend 194. The plug 202 and cartridge body 172 are sealed by means of an"O" ring 195.

It will be understood from the above that the rotation of the plug 202relative to the cartridge 172 bodily moves the plug 202 longitudinallyof the cartridge body 172 and moves the outer or free end of the stemportion 208 into and out of the ball chamber 192. If the fluid pressureat the ball chamber end 194 is lower than the fluid pressure at the end196 and the free end of the stem portion 208 is positioned within theball chamber 192, the stem portion free end engages the ball 174 andprevents it from seating against the contoured surface 178 of the end194. It will also be understood that by varying the distance that thestem portion free end is moved into the ball chamber 192, the positionalrelationship of the ball 174 and the ball chamber end 194 can be varied.In other words, adjustment means 176 moves the flow control element orball 174 between a position seating against surface 194 and preventingor blocking flow in a direction from end 196 to end 194 and a positionspaced from surface 194 by a selected amount to provide controlled ormetered flow in a direction from end 196 to end 194. When flow is in theopposite direction, i.e. from end 194 to end 196, the flow controlelement or ball 194 allows substantially free flow and is biased by thefluid pressure against pin 200 as shown in FIG. 3. As shown in FIG. 4,the exterior surface of the cartridge body 172 bears suitable indicia210 so that rotation of the knob portion 204 and thus the position ofthe stem portion free end within the ball chamber 192 and the distanceball 174 is spaced from surface 194 by action of the stem 208 can beselected.

Referring again to FIG. 1, there are shown two identical flow controlmeans 16,17 sealingly received by the access openings 98 and 100,respectively. The passageway portions 186,186 of the cartridge bodies172,172 are in flow communication with one another through the portion102 of the manifold bore 92, and the manifold bores 94 and 96 are incontrolled flow communication with one another through the passagewayportions 186,186. It follows that the first and second chambers 67,69 ofthe elongated cavity 66 are in controlled flow communication with oneanother through the passages defined by the housing means 12 and flowcontrol means 16,17 and that a continuous, controlled flow path forhydraulic fluid forced to move from one cavity chamber to the other isthereby provided.

In a damping operation of the damper 10 during which the clevises 20 and22 are forced to move toward one another in a compression mode so thatthe piston head 120 increases the fluid pressure within the secondchamber 69 and decreases the fluid pressure within the first chamber 67,hydraulic fluid is forced to exit the second chamber 69 and move to thefirst chamber 67. Hydraulic fluid exiting the second chamber 69 throughregion 112 and manifold 94 passes into the access opening 98 and intothe passageway portion 192 of the flow control means 16. In the ballchamber 192 of the flow control means 16, the ball 174 and outlet end194 cooperate to permit fluid to pass out of the flow control means 16at a controlled rate or metered. Passing out of the flow control means16 and into the portion 102 of the manifold bore 92, hydraulic fluidflows substantially unrestricted to the first chamber 67 by means of theflow control means 17, manifold bore 96, shock tube bore 68, and shocktube aperture 70. In this mode, ball 174 of flow control means 17 abutspin 200 thereby allowing substantially free flow in a direction intobore 96, the flow control means 17 operating like a check valve. It willbe understood that by controlling the positional relationship betweenthe ball 174 and ball chamber outlet end 194 of the flow control means16 by its adjustment means 176, the relative movement between the pistonhead 120 and cavity 66, and thus the damping effect of the damper 10, inthe compression mode is thereby controlled.

As discussed above, the volumes of the first and second cavity chambers67 and 69 vary at different rates as the head 120 reciprocates withinthe cavity 66. Accordingly, hydraulic fluid which exits the secondchamber 69 and cannot be accepted by the first chamber is forced intothe accumulator cavity 75 through the relief valve 104. Because theaccumulator cavity 75 contains the closed cell foam material 77,aeration of the hydraulic fluid entering the accumulator cavity 75 isprevented.

In a damping operation during which the damper clevises 20 and 22 areforced to move away from one another in a tension mode so that thepiston head increases the fluid pressure within the first chamber 67 anddecreases the fluid pressure within the second chamber 69, hydraulicfluid is forced to exit the first chamber 67 and move to the secondchamber 69. Hydraulic fluid exits the first chamber 67 through opening70 and flows along passage 68 and along manifold bore 96 into the secondaccess opening 100 and into the passageway portion 192 of the flowcontrol means 17. In the ball chamber 192 of the flow control means 17,the ball 174 and outlet end 194 cooperate to permit fluid to pass out ofthe flow control means 17 at a controlled or metered rate. Passing outof the flow control means 17 and into the portion 102 of the manifoldbore 92, hydraulic fluid flows substantially unrestricted to the secondchamber 69 by means of the flow control means 16 and manifold bore 94.In this mode, ball 174 of flow control means 16 abuts pin 200 therebyallowing substantially free flow in a direction into bore 94, the flowcontrol menas 16 operating like a check valve. Since the second chamber69 accepts more hydraulic fluid than the first chamber 67 can supplyduring the tension mode, fluid is drawn out of the accumulator cavitythrough the relief valve 104 and flows through control means 16 intomanifold bore 94. It will be understood from the above that bycontrolling the positional relationship between the ball 174 and ballchamber outlet end 194 of the flow control means 17 by its adjustmentmeans 176, the relative movement between the piston head 120 and cavity66, and thus the damping effect of the damper 10, in the tension mode isthereby controlled.

The aforedescribed damper 10 is advantageous in that the flow controlmeans 16 and 17 permit independent control of the damping effects of thedamper 10 when operating in its compression and tension modes.Furthermore, because the flow control means 16 and 17 are eachself-contained units or cartridges containing the flow-control portionof the network of flow passages, the flow control means 16,17 can eachbe easily separated or removed from the remainder of the damper 10 forpurposes of cleaning or repairing the flow control means 16 or 17 or foraltering the flow control characteristics of the passageway portion 186of the cartridge body 172. These latter alterations can be effected bymodifying the shape or configuration of the ball chamber inlet end 194.To alter the rate of change of positional relationship between the ball174 and ball chamber inlet end 194 as the knob portion 204 is rotatedwithin the cartridge body 172, the pitch of the meshed threads of thecartridge body 172 and plug 202 can be modified.

Thus, the orifice ball 174 not only serves as a metering device butlikewise as a check valve relief device. Flow through the meteringcartridge 16,17 is orificed when the flow direction is from the orificeball end and is free flow in the opposite direction, since it unseatsthe orifice ball 174. This dual function provides the desired damping inone direction and also insures rapid refill of the evacuated chamberwhen flow is in the opposite direction. The dual function of thisorifice ball 174 eliminates the need for additional internal valving inthe damper 10. The arrangement of passages or bores in manifold 30 issuch that when tension motion takes place, the tension meteringcartridge acts as a damping device, and the compression meteringcartridge acts as a relief device. Conversely, when compression motiontakes place, the compression metering cartridge acts as a damping deviceand the tension metering cartridge acts as a relief device. Since bothof these metering cartridges 16,17 are identical, it is essential thatthe flow path design of manifold 30 be of a nature as to permit thisdual function. The feature of independent tension and compressionmetering cartridges provides the unique ability to furnish the damperwith tension damping and compression damping, tension damping and freeflow compression motion, or compression damping and free flow tensionmotion. The latter two modes are accomplished by a form of flow controlmeans which now will be described.

With reference to FIG. 5, there is shown another embodiment of flowcontrol means, indicated 216, in accordance with the present invention.The flow control means 216 includes a cartridge body 218 having a capportion 220, a threaded portion 222, and an extended portion 224. Thethreaded portion 222 is adapted to be threadably received by the threadsof the damper access opening 98 or 100 with the extended portion 224extending into the opening 98 or 100. "O" rings 226 and 228 contributeto the seal between the walls of the opening 98 or 100 and the cartridgebody 218.

The extended portion 224 of the flow control means 216 defines anelongated aperture 230 extending longitudinally of the portion 224 andopening at the free end thereof. A small bore 232 extends transverselyinto the extended portion 224, and another, slightly larger bore 234extends transversely through the extended portion 224. Both of thespaced-apart bores 232 and 234 intersect the elongated aperture 230, andbore 234 is located nearest the threaded portion 222.

The elongated aperture 230 defines a ball chamber 236 within which aflow control element in the form of spherical ball 240 is looselyreceived. The ball chamber 236 includes a first conically-shaped end 242and a second relatively large end 244, the ends 242 and 244 being flowinlet or outlet ends depending upon the direction of flow as will bedescribed. When the fluid pressure at the first end 244 exceeds thefluid pressure at the second end 242, the ball 240 is biased intoengagement with the end 242 so that fluid is prevented from exiting theball chamber 236 through the end 242. The spherical ball 240 is coatedwith a resilient elastomer, such as urethane, so as to provide a softseat and effective seal between the inlet end 242 and ball 240. A stopmeans in the form of pin 246 is mounted across the end 244 to preventthe ball 240 from exiting the ball chamber 236. When the fluid pressureat the end 242 exceedes the fluid pressure at the end 244, the ball isbiased into contact with the pin 246 and fluid is permitted to flowsubstantially unrestricted between the ball 240 and the walls of theball chamber 236 and out of the chamber end 244.

With reference to FIG. 6, there is shown an alternative embodiment of adamper 260 within which is utilized flow control means 216 of FIG. 5 andflow control means 17 of FIGS. 1 and 3. Other components of the damper260 which correspond to components of the damper 10 of FIG. 1 areaccordingly given the same reference numerals. As shown in FIG. 6, theenlogated opening 230 of the flow control means 216 communicates withthe interior of the access opening 98 through the end 244 of the ballchamber and through the small bore 232, and the bore 234 of controlmeans 216 communicates with the portion 102 of the manifold bore 92.

In a compression mode operation of the damper 260 of FIG. 6 during whichthe damper piston head increases the fluid pressure within the secondchamber 69 and decreases the fluid pressure within the first chamber 67(FIG. 1), hydraulic fluid is forced to exit the second chamber 69 andmove to the first chamber 67. Inasmuch as the fluid pressure decreasesfrom the second chamber to the first through the network of flowpassages provided by housing means 12, manifold 30 and flow controlmeans 216,17 fluid pressure at the ball chamber end 244 is greater thanthe fluid pressure at the end 242 of control means 216 (FIG. 5) so thatthe ball 240 is forced to seat in the inlet end 242 and prevent fluidflow through the ball chamber 236. The small bore 232, however, permitshydraulic fluid to enter the elongated aperture 230 and out of thecartridge body 218 through the bore 234. Passing out of the flow controlmeans 216 and into the manifold bore portion 102, hydraulic fluid flowssubstantially unrestricted to the first chamber 67. In particular, fluidflows from manifold bore portion 102 through control means 17 with theball 174 thereof allowing substantially free flow and into manifoldpassage 96 and through passage 68 and opening 70 into chamber 67.

It will be understood from the above that control of the hydraulic fluidflow of the damper 260 during a compression mode, and thus the dampingeffect of the damper 260, is maintained by the size and shape of thesmall bore 232. The smaller the size of the bore 232, the higher thecushioning effect of the damper 260, and the larger the size of the bore232, the lower the cushioning effect of the damper 260. The flow controlmeans 216 is thereby a means for fixing the damping effect of the damper260 in that once the control means 216 is installed, the damping effectof the damper 260 in a compression mode cannot be changed.

In a tension mode operation of the damper 260 of FIG. 6 during which thedamper piston increases the fluid pressure within the first chamber 67(FIG. 1) and decreases the fluid pressure within the second chamber 69,hydraulic fluid is forced to exit the first chamber 67 and move to thesecond chamber 69. Inasmuch as the fluid pressure decreases from thefirst chamber 67 to the second chamber 69 through the network of flowpassages provided by the damper housing means 12, manifold 30 and flowcontrol means 216,17, the fluid pressure at the ball chamber end 242 isgreater than the fluid pressure at the opposite end 244. Consequently,the ball 240 moves into engagement with the pin 246 mounted in the ballchamber outlet end and hydraulic fluid is permitted to passsubstantially unrestricted through the elongated aperture 230. Controlover the damping effect of the damper 260 during a tension mode ismaintained by the adjustable flow control means 17 discussed above.

The fixed flow control means 216 of FIGS. 5 and 6 may be preferred overthe adjustable flow control means 16 or 17 of FIGS. 1 and 3 inapplications where the damping effects of a damper need not be alteredor should not be. The fixed flow control means 216 thus providessuitable means preventing the altering of damping effects until thecartridge body 218 is removed or separated from the remainder of adamper.

It will also be understood that any two of several combinations ofadjustable flow control means and fixed control means in accordance withthis invention can be used within a damper of the aforedescribedconstruction in order to provide any of a number of damping effects. Forexample, inasmuch as the damper 260 of FIG. 6 has adjustable damping intension and fixed damping in compression, the position of the twocontrol means 216,17 can be exchanged so as to provide so as to providethe resulting damper with adjustable damping in compression and fixeddamping in tension. Furthermore, inasmuch as the damper 10 of FIGS. 1, 2and 4 has adjustable damping on both tension and compression, theadjustable control means 16 and 17 can be easily replaced with fixedcontrol means similar in structure to control means 216 of FIGS. 5 and 6to provide the resultant damper with fixed damping in both tension andcompression.

In applications in which a damper having fixed damping effect in onemode is desired, an adjustable flow control means in accordance withthis invention can be initially used with the damper and adjusted untilthe desired damping effect in the one mode is obtained. The adjustableflow control means can then be replaced with a fixed control means toprovide fluid flow control corresponding to that provided by desiredadjustment of the adjustable flow control means.

With reference to FIG. 7, there is shown a plug 250 having a cap portion252, threaded portion 254 and "0" ring 256 adapted to be sealinglyaccepted by the threaded portion of a damper access opening 98 or 100.When installed in either access opening 98 or 100, substantiallyunrestricted fluid flow is permitted in either direction through theaccess opening 98 or 100. Thus, plug 250 may be utilized in a damper inwhich substantially unrestricted flow, and subsequently little dampingeffect, is desired in either a tension or a compression mode.

While the present invention has been described in a number ofillustrative embodiments, it will be understood that numerousmodification and substitutions can be employed without departing fromthe spirit of the invention. For example, although the damper 10 hasbeen described as having adjustable flow control means 16, 17 which canbe manually adjusted by rotating the knob portions 176,176 thereof, itwill be understood that adjustments of the damping effects of the damper10 can be controlled automatically and remotely of the damper 10. Thecontrol schematic of FIG. 8 illustrates the adjusting operation of thedamper 10 by means of two reversible motors 261,262 which can bestepping motors. The output shaft of each motor is connected to the knobof a corresponding one to the control means. Both of the motors 261,262are operated by a control 264 which can be at a remote location ifdesired. By independently energizing the motors 261,262 to rotate in onedirection or the other in response to signals sent to it from thecontrol 264, the knobs 176,176 of the flow control means are rotated toadjust the damping effects of the damper 10 in both tension andcompression modes. Furthermore, only one flow control means can be motoroperated, if desired especially in the situation where the other flowcontrol means is of the fixed type.

It is therefore apparent that the present invention accomplishes itsintended objects. While embodiments of the present invention have beendescribed in detail, that is for the purpose of illustration, notlimitation.

I claim:
 1. A damper for acting between two relatively movable objectscomprising:a) housing means adapted to be operatively connected to oneof said objects; b) piston means comprising a head positioned withinsaid housing means and a rod extending from said housing means adaptedto be operatively connected to the other of said objects; c) saidhousing means including means defining an elongated cavity forcontaining hydraulic fluid, said piston head being received by saidcavity so as to separate said cavity into a first variable-volumechamber and a second variable-volume chamber and adapted to slidablemove relative to and along the length of said elongated cavity andthereby vary the volumes of said first and second chambers in responseto relative movement between said two objects, said housing meansfurther including means defining first and second access openings, afirst passage, a second passage and a third passage, said first chambercommunicating with said first access opening through said first passage,said second chamber communicating with said second access openingthrough said second passage, and said first and second access openingsbeing in communication through said third passage; d) first and secondhydraulic fluid flow control means each including first and secondbodies sealingly accepted by said first and second access openings,respectively, each of said bodies defining a passageway therethroughproviding flow communication between the particular ones of said first,second and third passages in communication with the corresponding onesof said access openings and thereby providing a flow path for hydraulicfluid forced to flow between said first and second chambers as thevolumes of said chambers are varied by said relative movement of saidtwo objects, each of said first and second control means furtherincluding means associated with said first and second body passagewaysfor metering the flow of hydraulic fluid in one direction through saidpassageway so that as hydraulic fluid is forced to flow through saidpassageway in said one direction, the damping effect of said damper iscontrolled and for allowing substantially unrestricted flow of hydraulicfluid in other direction whereby when tension motion of said dampertakes place said first and second flow control means act in damping andrelief modes and when compression motion takes place, the opposite onesof said first and second control means act in damping and relief modes,said first and second metering means being in said first and secondbodies, respectively; e) said means associated with said body passagewayof said first hydraulic fluid flow control means including a flowcontrol element in said first body freely movable in said first bodypassageway between a first position blocking fluid flow in said onedirection and a second position allowing free flow in the oppositedirection, adjustment means in said first body operatively contactingsaid flow control element for varying the location of said flow controlelement relative to said first position thereby metering the fluid flowin said one direction, and stop means in said first body for engagingsaid flow control element at said second position during free flow inthe opposite direction; f) said means associated with said bodypassageway of said second hydraulic fluid flow control means including aflow control element in said second body freely movable in said secondbody passageway between one position blocking fluid flow in saidopposite direction and another position allowing free flow in said onedirection, adjusting means in said second body operatively contactingsaid flow control element in said second body for varying the locationof said flow control element in said second body relative to said oneposition thereby metering the fluid flow in said opposite direction, andstop means in said second body for engaging said flow control element insaid second body at said another position during free flow in said onedirection; and g) said body of each of said flow control means includingsaid passageway, said flow control element, said adjustment means andsaid stop means being independently releasably accepted by acorresponding one of said access openings so as to permit said first andsecond flow control means to be easily and independently separated fromthe remainder of said damper so that each flow control means can becleaned, repaired and modified without disassembly of the remainder ofsaid damper.
 2. A damper for acting between two relatively movableobjects comprising:a) housing means adapted to be operatively connectedto one of said objects; b) piston means comprising a head within saidhousing means and a rod extending from said housing means and adapted tobe operatively connected to the other of said objects; c) said housingmeans including means defining an elongated cavity for containinghydraulic fluid, said piston head being received by said cavity so as toseparate said cavity into a first variable-volume chamber and a secondvariable-volume chamber and adapted to slidably move relative to andalong the length of said elongated cavity and thereby vary the volumesof said first and second chambers in response to relative movementbetween said two objects, said housing means further including meansdefining first and second access openings, a first passage, a secondpassage and a third passage, said first chamber communicating with saidfirst access opening through said first passage, said second chambercommunicating with said second access opening through said secondpassage, and said first and second access openings being incommunication through said third passage; d) a first hydraulic fluidflow control means including a first body sealingly accepted by one ofsaid first and second access openings and defining a passagewaytherethrough providing flow communication between the particular ones ofsaid first, second and third passages in communication with one of saidaccess opening and thereby providing a flowpath for hydraulic fluidforced to flow therebetween, said first flow control means furtherincluding means associated with said first body passageway foradjustably metering the flow of hydraulic fluid in one direction throughsaid first body passageway so that as hydraulic fluid is forced to flowthrough said first body passageway in said one direction, the dampingeffect of said damper is controlled and for allowing substantiallyunrestricted flow of hydraulic fluid in the other direction; e) a secondhydraulic fluid flow control means including a second body sealinglyaccepted by the other of said first and second access openings anddefining a passageway therethrough providing flow communication betweenthe particular ones of said first, second and third passages incommunication with said other access opening and thereby providing aflowpath for hydraulic fluid forced to flow therebetween, said secondflow control means further including means associated with said secondbody passageway for fixedly metering the flow of hydraulic fluid throughsaid second body passageway in said other direction through said secondbody passageway so that as hydraulic fluid is forced to go through saidsecond body passageway in said other direction, the damping effect ofsaid damper is controlled and for allowing substantially unrestrictedflow of hydraulic fluid in said one direction so that said first andsecond flow control means provide a flow path for hydraulic fluid forcedto flow between said first and second chambers as the volumes of saidchambers are varied by the relative movement of said two objects wherebysaid first flow control means provides adjustable tension damping orcompression damping depending upon which each access opening it is inand said second flow control means provides fixed compression damping ortension damping depending upon which access opening it is in; and f)said body of each of said first and second flow control means beingindependently releasably accepted by a corresponding one of said accessopenings so as to permit either of said flow control means to be easilyand independently separated from the remainder of said damper.
 3. Adamper according to claim 2, wherein said first hydraulic fluid flowcontrol means comprises a flow control element freely movable in saidpassageway between a first position blocking fluid flow in said onedirection and a second position allowing free flow in the oppositedirection, adjustment means operatively contacting said flow controlelement for varying the location of said flow control element relativeto said first position thereby metering the fluid flow in said onedirection, and stop means for engaging said flow control element at saidsecond position during free flow in the opposite direction and whereinsaid second hydraulic fluid flow control means comprises a chamberincluded in said second passageway and having a flow inlet and a flowoutlet end and a flow control element received by said chamber, saidelement adapted to be biased toward the chamber inlet or outlets endhaving the lower fluid pressure, one of said inlet and outlet ends beingof such a conformation that when hydraulic fluid pressure is lower atsaid one end than the fluid pressure at the other end, said flow controlelement and said one end cooperate to controllably restrict the flow ofhydraulic fluid through said passageway, and the other of said inlet andsaid outlet ends being of such a conformation that when hydraulic fluidpressure is lower at said other end than the fluid pressure at said oneend, said flow control element and said other end co-operate to permitsubstantially unrestricted flow of hydraulic fluid through said secondpassageway.
 4. A damper for acting between two relatively movableobjects comprising:housing means adapted to be operatively connected toone of said objects; piston means comprising a head within said housingmeans and a rod extending from said housing means adapted to beoperatively connected to the other of said objects, said housing meansincluding means defining an elongated cavity for containing hydraulicfluid, said piston head being received by said cavity so as to separatesaid cavity into a first variable-volume chamber and a secondvariable-volume chamber and adapted to slidably move relative to andalong the length of said elongated cavity and thereby vary the volumesof said first and second chambers in response to relative movementbetween said two objects toward and away from one another, said housingmeans further including means defining a first access opening, a firstpassage and a second passage, said first chamber communicating with saidaccess opening through said first passage and said second chambercommunicating with said access opening through said second passage;first hydraulic fluid flow control means including a body sealinglyaccepted by said access opening and defining a passageway therethroughproviding flow communication between said first and second passages andthereby providing a flow path for hydraulic fluid forced to flow betweensaid first and second chambers as the volumes of said chambers arevaried by said relative movement of said two objects toward and awayfrom one another, said flow control means further including means insaid body and associated with said body passageway for controlling theflow of hydraulic fluid in one direction through said passageway so thatas hydraulic fluid is forced to flow through said passageway in said onedirection, the damping effect of said damper is controlled, saidpassageway including a chamber having a flow inlet end and flow outletend and said means associated with said passageway including a flowcontrol element in said body and received by said chamber, said flowcontrol element adapted to be biased toward the chamber inlet or outletend having the lower fluid pressure, one of said inlet and said outletends being of such a conformation that when hydraulic fluid pressure islower at said one end than the fluid pressure at the other end, saidflow control element and said one end cooperate to controllably restrictthe flow of hydraulic fluid through said passageway and the other ofsaid inlet and said outlet ends being of such a conformation that whenhydraulic fluid pressure is lower at said other end than the fluidpressure is lower at said other end than the fluid pressure at said oneend, said flow control element and said other end cooperate to permitsubstantially unrestricted flow of hydraulic fluid through saidpassageway, said one end of said chamber defining a contoured surface ofsuch configuration that flow of hydraulic fluid through said one end iscontrolled by controlling the positional relationship of said flowcontrol element to said contoured surface and said flow control meansincluding adjustment means in said body for adjusting the positionalrelationship of said flow control element to said contoured surface ofsaid one end, said adjustment means including flow control elementcontacting means mounted for movement relative to and within said bodypassageway for moving said flow control element relative to saidcontoured surface between one positional relationship with and withinsaid chamber and another such positional relationship, said body of saidcontrol means defining an elongated opening extending therethrough, saidelongated opening having one portion defining at least a portion of saidpassageway and having another portion, said adjustment means includingan adjustment portion and a stem portion extending from said adjustmentportion, said adjustment portion being movably and adjustably mounted insaid another portion of said elongated opening for adjustable movementof said adjustment means relative to and along the length of saidelongated opening as said adjustment portion is moved relative to saidbody of said control means, and said stem portion extending from saidadjustment portion and into said chamber for contacting said flowcontrol element for moving said flow control element between said onepositional relationship with said contoured surface and another as saidadjustment portion is moved relative to said body; said first controlmeans controlling hydraulic fluid flow in one direction between saidfirst and second chambers, said housing means including means defining asecond access opening arranged in fluid communication with saidpassageway of said first control means, with said first passage and withsaid second passage, and said damper further comprising a secondhydraulic fluid flow control means including a body sealingly acceptedby said second access opening and defining a passageway through saidbody of said second flow control means providing flow communicationbetween said first and second passages and thereby providing a flow pathfor hydraulic fluid forced to flow between said first and secondchambers, said second flow control means further including means in saidbody of said second flow control means and associated with passagewaysfor controlling the flow of hydraulic fluid therethrough in thedirection opposite said one direction so that as hydraulic fluid isforced to flow through said passageway of said second flow controlmeans, in said opposite direction, the damping effect of said damper iscontrolled; said means associated with said body passageway of saidsecond flow control means comprising a flow control element in said bodyof said second flow control means and freely movable in said passages ofsaid second flow control means between a first position blocking fluidflow in said one direction and a second position allowing free flow inthe opposite direction, adjustment means in said body of said secondflow control means operatively contacting said flow control element insaid body of said second flow control means relative to said firstposition thereby metering the fluid flow in said one direction, and stopmeans in said body of said second flow control means for engaging saidflow control element in said body of said second flow control means atsaid second position during free flow in the opposite direction; andsaid body of each of said flow control means including said passageway,said flow control element, said adjustment means and said stop meansbeing independently releasably accepted by a corresponding one of saidaccess openings so as to permit said first and second flow control meansto be easily and independently separated from the remainder of saiddamper so that each flow control means can be cleaned, repaired andmodified without disassembly of the remainder of said damper.
 5. Adamper as defined in claim 4 wherein said passageway of said second flowcontrol means includes a chamber having a flow inlet end and a flowoutlet end and said means associated with said passageway of said secondflow control means includes a flow control element received by saidchamber of said second flow control means, said flow control element ofsaid second flow control means adapted to be biased toward the chamberinlet or outlet end having the lower fluid pressure, one of said inletand said outlet ends of said chamber of said second flow control meanseach being of such a conformation that when hydraulic fluid pressure islower at said one end than the fluid pressure at the other end, saidflow control element of said second flow control means and said one endcooperate to controllably restrict the flow of hydraulic fluid throughsaid passageway of said second flow control means, and the other of saidinlet and said outlet ends of said chamber of said second flow controlmeans being of such a conformation that when hydraulic fluid pressure islower at said other end than the fluid pressure at said one end, saidflow control element of said second flow control means and said otherend cooperate to permit substantially unrestricted flow of hydraulicfluid through said passageway of said second flow control means.
 6. Adamper as defined in claim 5 wherein said one end of said chamber ofsaid second flow control means defines a contoured surface of suchconfiguration that flow of hydraulic fluid through said one end iscontrolled by controlling the positional relationship of said flowcontrol element of said second flow control means to said contouredsurface and said second flow control means includes adjustment means foradjusting the positional relationship of said flow control element ofsaid second flow control means to said contoured surface of said oneend.
 7. A damper as defined in claim 6 wherein said adjustment means ofsaid second flow control means includes flow control element engagingmeans mounted for movement relative to and within said body passagewayof said second flow control means for moving said flow control elementof said second flow control means relative to said contoured surfacebetween one positional relationship with and within said chamber of saidsecond flow control means and another.
 8. A damper as defined in claim6, further including means for releasably locking the position of saidflow control element engaging means of said second flow control meansrelative to said body of said second flow control means thereby toreleasably hold the positional relationship of said flow control elementof said second flow control means to said contoured surface.
 9. A damperas defined in claim 5 wherein said chamber of said second flow controlmeans provides a first conduit portion of said passageway of said secondflow control means, said one end of said chamber of said second flowcontrol means is adapted to sealingly accept said flow control elementof said second flow control means when the fluid pressure at said oneend is lower than the fluid pressure at said other end, said passagewayof said second flow control means includes a second conduit portionarranged in parallel flow relation with said first conduit portion sothat when the fluid pressure at said one end is lower than the fluidpressure at said other end, said flow control element of said secondflow control means is sealingly accepted by said one end and the entireflow of hydraulic fluid in said one direction through said passageway ofsaid second flow control means is directed through said second conduitportion.
 10. A damper as defined in claim 9 wherein said second conduitportion is provided by an aperture of predetermined shape size forcontrollably restricting the flow of hydraulic fluid when said flow isentirely directed through said second conduit portion.
 11. A damper asdefined in claim 5, wherein said flow control element of said secondflow control means is coated with a resilient elastomer.
 12. In a damperfor acting between two objects subject to relative movement including ahousing assembly defining an elongated cavity for containing hydraulicfluid, a piston assembly including a head slidably received by saidcavity and separating said cavity into a first chamber and a secondchamber and means supported by said housing defining a flow passagecommunicating between said first chamber and said second chamber, saidhousing and said piston assembly adapted to be operatively connected toa corresponding one of said two objects so that as said two objects moverelative to each other, said piston head reciprocates in said cavity andforces hydraulic fluid to flow through said flow passage between saidfirst and second chambers, an improved flow control means operativelyassociated with said flow passage defining means and including:a) a bodydefining a passageway portion of said flow passage and means associatedwith said passageway portion for metering the flow of hydraulic fluid inone direction through said passageway portion so that as hydraulic fluidis forced to flow through said passageway portion in said one direction,the damping effect of said damper is controlled, and for allowingsubstantially unrestricted flow of hydraulic fluid in the otherdirection through said passageway portion; b) said housing includingmeans defining an access opening; c) said body of flow control meansbeing releasably accepted by said access opening so as to permit saidflow control means to be easily separated from the remainder of thedamper; d) said passageway portion including a ball chamber having aflow inlet end and a flow outlet end and said means associated with saidpassageway portion including a spherical ball received by said ballchamber, said ball adapted to be biased by the flow of hydraulic fluidtoward the ball chamber inlet or outlet end having the lower fluidpressure, one of said inlet and said outlet ends being of such aconformation that when hydraulic fluid pressure is lower at said one endthan the fluid pressure at the other end, said ball and said one endcooperate to controllably restrict the flow of hydraulic fluid throughsaid passageway portion, and the other end of said inlet and outlet endsbeing of such a conformation that when hydraulic fluid pressure is lowerat said other end than the fluid pressure at said one end, said ball andsaid other end cooperate to permit substantially unrestricted flow ofhydraulic fluid through said passageway; e) said ball chamber providinga first conduit portion of said passageway portion, said one end of saidball chamber being adapted to sealing accept said ball when the fluidpressure at said one end is lower than the fluid pressure at said otherend, and said passageway portion includes a second conduit portionarranged in parallel flow relation with said first conduit portion sothat when the fluid pressure at said one end is lower than the fluidpressure at said other end, said ball is sealingly accepted by said oneend and the entire flow of hydraulic fluid in said one direction throughsaid passageway is directed through said second conduit portion, saidsecond conduit portion being provided by an aperture of predeterminedshape and size for controllably restricting the flow of hydraulic fluidwhen said flow is entirely directed through said second conduit portion.13. A damper as defined in claim 12, wherein said body of said flowcontrol means including said passageway, said contoured surface, saidball chamber, said ball and said aperture is releasably accepted by saidaccess opening so as to permit said flow control means to be easilyseparated from the remainder of the damper so that said flow controlmeans can be cleaned, repaired and modified without dissassembly of theremainder of said damper.